Linux防火墙之iptables匹配条件
上一篇博文我们说到了iptables的基本工作原理、数据报文在内核的走向和管理链、管理规则、以及查看规则、导入和导出规则；回顾请参考https://www.cnblogs.com/qiuhom-1874/p/12237976.html，今天我们再来说说iptables的基本匹配条件。
iptables的基本匹配条件也叫通用匹配条件，是iptables/netfilter原生自带的，无需加载模块，通俗的讲就是iptables这个命令的原生选项。iptables基本匹配条件有以下几种
一、iptables的基本匹配条件
上一篇博文我们说到了iptables的基本工作原理、数据报文在内核的走向和管理链、管理规则、以及查看规则、导入和导出规则；回顾请参考https://www.cnblogs.com/qiuhom-1874/p/12237976.html，今天我们再来说说iptables的基本匹配条件。
iptables的基本匹配条件也叫通用匹配条件，是iptables/netfilter原生自带的，无需加载模块，通俗的讲就是iptables这个命令的原生选项。iptables基本匹配条件有以下几种
1、[!] -s,--source addresss[/mask][,…]：表示匹配报文段源ip地址或范围，它可以是一个ip地址，也可以是一个网段地址，网段地址需要写明子网掩码，其中子网掩码支持225.255.0.0的方式，也支持数字表示，比如192.168.0.0/24。同时它也支持取反。
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
461 33551 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
134 11256 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 14 packets, 1320 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 192.168.0.99 0.0.0.0/0 tcp spt:53
134 11256 ACCEPT icmp -- * * 192.168.0.99 0.0.0.0/0 icmptype 0
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]# iptables -A my_chain -s 192.168.1.0/24 -j ACCEPT
[root@test ~]# iptables -A my_chain -s 192.168.0.232 -d 192.168.0.99 -j ACCEPT
[root@test ~]# iptables -A my_chain -s 192.168.0.0/255.255.255.0 -j ACCEPT
[root@test ~]# iptables -nvL my_chain
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT all -- * * 192.168.1.0/24 0.0.0.0/0
0 0 ACCEPT all -- * * 192.168.0.232 192.168.0.99
0 0 ACCEPT all -- * * 192.168.0.0/24 0.0.0.0/0
[root@test ~]# iptables -A my_chain ! -s 192.168.10.0/24 -j ACCEPT
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
946 67475 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
134 11256 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 15 packets, 1396 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 192.168.0.99 0.0.0.0/0 tcp spt:53
134 11256 ACCEPT icmp -- * * 192.168.0.99 0.0.0.0/0 icmptype 0
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT all -- * * 192.168.1.0/24 0.0.0.0/0
0 0 ACCEPT all -- * * 192.168.0.232 192.168.0.99
0 0 ACCEPT all -- * * 192.168.0.0/24 0.0.0.0/0
0 0 ACCEPT all -- * * !192.168.10.0/24 0.0.0.0/0
[root@test ~]#
2、-d,--destination address[/mask][,…]：表示匹配报文的目标ip地址或范围，它同-s的用法一样，支持单台主机或一个网段，网段需写明子网掩码，子网掩码支持数字表示，也支持子网掩码地址的方式表示。同时它也支持对匹配的条件取反。
[root@test ~]# iptables -F my_chain
[root@test ~]# iptables -nvL my_chain
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]# iptables -A my_chain -d 192.168.0.99 -p tcp --dport 22 -j ACCEPT
[root@test ~]# iptables -A my_chain -d 192.168.0.10 -p tcp --dport 3306 -j DROP
[root@test ~]# iptables -A my_chain -d 192.168.10.0/24 -p tcp --dport 25 -j DROP
[root@test ~]# iptables -A my_chain ! -d 192.168.11.0/255.255.255.0 -p tcp --dport 123 -j DROP
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
1698 123K ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
134 11256 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 17 packets, 1580 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 192.168.0.99 0.0.0.0/0 tcp spt:53
134 11256 ACCEPT icmp -- * * 192.168.0.99 0.0.0.0/0 icmptype 0
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:22
0 0 DROP tcp -- * * 0.0.0.0/0 192.168.0.10 tcp dpt:3306
0 0 DROP tcp -- * * 0.0.0.0/0 192.168.10.0/24 tcp dpt:25
0 0 DROP tcp -- * * 0.0.0.0/0 !192.168.11.0/24 tcp dpt:123
[root@test ~]#
3、[!] -p, --protocol protocol：指定协议，可使用数字如0（all）；protocol: tcp, udp, icmp, icmpv6, udplite,esp, ah, sctp, mh or“all“ 参考：/etc/protocols
[root@test ~]# iptables -F my_chain
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
1752 126K ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
134 11256 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 13 packets, 1212 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 192.168.0.99 0.0.0.0/0 tcp spt:53
134 11256 ACCEPT icmp -- * * 192.168.0.99 0.0.0.0/0 icmptype 0
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]# iptables -A my_chain -s 192.168.0.232 -d 192.168.0.99 -p tcp --dport 80 -j DROP
[root@test ~]# iptables -A my_chain -s 192.168.0.232 -d 192.168.0.99 -p tcp --dport 23 -j DROP
[root@test ~]# iptables -A my_chain -d 192.168.0.99 -p tcp --sport 25 -j ACCEPT
[root@test ~]# iptables -A my_chain -d 192.168.0.99 -p icmp --icmp-type 0 -j ACCEPT
[root@test ~]# iptables -A my_chain -s 192.168.0.232 -d 192.168.0.99 -p icmp --icmp-type 8 -j ACCEPT
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
2487 179K ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
134 11256 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 47 packets, 4340 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 192.168.0.99 0.0.0.0/0 tcp spt:53
134 11256 ACCEPT icmp -- * * 192.168.0.99 0.0.0.0/0 icmptype 0
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
0 0 DROP tcp -- * * 192.168.0.232 192.168.0.99 tcp dpt:80
0 0 DROP tcp -- * * 192.168.0.232 192.168.0.99 tcp dpt:23
0 0 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp spt:25
0 0 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 0
0 0 ACCEPT icmp -- * * 192.168.0.232 192.168.0.99 icmptype 8
[root@test ~]# iptables -A my_chain ! -p udp -j ACCEPT
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
2586 186K ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
134 11256 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 13 packets, 1212 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 192.168.0.99 0.0.0.0/0 tcp spt:53
134 11256 ACCEPT icmp -- * * 192.168.0.99 0.0.0.0/0 icmptype 0
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
0 0 DROP tcp -- * * 192.168.0.232 192.168.0.99 tcp dpt:80
0 0 DROP tcp -- * * 192.168.0.232 192.168.0.99 tcp dpt:23
0 0 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp spt:25
0 0 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 0
0 0 ACCEPT icmp -- * * 192.168.0.232 192.168.0.99 icmptype 8
0 0 ACCEPT !udp -- * * 0.0.0.0/0 0.0.0.0/0
[root@test ~]#
提示：-p指定某一协议时，往往会有该协议的一些隐式扩展的选项，比如我们指定-p tcp 表示指定协议类型为tcp 后面指定的源端口或者目标端口 就是tcp模块的隐式。通俗讲就是我们指定了协议为tcp 可以不用明确的用-m 再指定其模块，这种机制我们叫隐式扩展。上面的例子用到了隐式扩展到有 tcp 的 --sport --dport ;icmp 协议的--icmp-type;当然-p指定协议的类型也可以用！ 来对它取反，表示匹配除了指定的协议以为的所有协议的报文，如果不用-p 指定协议表示匹配所有协议的报文
4、[!] -i, --in-interface name：报文流入的接口；只能应用于数据报文流入环节，只应用于INPUT、FORWARD、PREROUTING链以及自定义链。
[root@test ~]# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: enp2s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 00:30:18:51:af:3c brd ff:ff:ff:ff:ff:ff
inet 192.168.0.99/24 brd 192.168.0.255 scope global noprefixroute enp2s0
valid_lft forever preferred_lft forever
inet 172.16.1.2/16 brd 172.16.255.255 scope global noprefixroute enp2s0:0
valid_lft forever preferred_lft forever
inet6 fe80::230:18ff:fe51:af3c/64 scope link
valid_lft forever preferred_lft forever
3: enp3s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN group default qlen 1000
link/ether 00:30:18:51:af:3d brd ff:ff:ff:ff:ff:ff
4: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default
link/ether 02:42:63:ab:82:55 brd ff:ff:ff:ff:ff:ff
inet 172.17.0.1/16 scope global docker0
valid_lft forever preferred_lft forever
[root@test ~]# iptables -F my_chain
[root@test ~]# iptables -nvL my_chain
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]# iptables -A my_chain -s 192.168.0.0/24 -i enp2s0 -j ACCEPT
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
2911 209K ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
134 11256 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 13 packets, 1212 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 192.168.0.99 0.0.0.0/0 tcp spt:53
134 11256 ACCEPT icmp -- * * 192.168.0.99 0.0.0.0/0 icmptype 0
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT all -- enp2s0 * 192.168.0.0/24 0.0.0.0/0
[root@test ~]# iptables -A OUTPUT -i enp2s0 -j ACCEPT
iptables v1.4.21: Can't use -i with OUTPUT
Try `iptables -h' or 'iptables --help' for more information.
[root@test ~]#
提示：自定义添加到规则可以被任意主链所引用。不存在自定义链上的规则不适用主链，但主链上可以引用它的，只是说主链引用后，规则不生效，匹配不到报文。-i 表示指定网络报文流入的接口，所以这个基本匹配条件，只能用于报文能够进来的链上，比如PREROUTING、INPUT、FORWARD这三个主链，以及自定义链，通常情况，如果写到自定义链，都是被这三个主链所引用，除此之外，被OUTPUT、和POSTROUTING所引用，规则是无效的，不能匹配到报文。
5、[!] -o, --out-interface name：报文流出的接口；只能应用于数据报文流出的环节，只应用于FORWARD、OUTPUT、POSTROUTING链以及自定义链
[root@test ~]# ip a s
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: enp2s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 00:30:18:51:af:3c brd ff:ff:ff:ff:ff:ff
inet 192.168.0.99/24 brd 192.168.0.255 scope global noprefixroute enp2s0
valid_lft forever preferred_lft forever
inet 172.16.1.2/16 brd 172.16.255.255 scope global noprefixroute enp2s0:0
valid_lft forever preferred_lft forever
inet6 fe80::230:18ff:fe51:af3c/64 scope link
valid_lft forever preferred_lft forever
3: enp3s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN group default qlen 1000
link/ether 00:30:18:51:af:3d brd ff:ff:ff:ff:ff:ff
4: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default
link/ether 02:42:63:ab:82:55 brd ff:ff:ff:ff:ff:ff
inet 172.17.0.1/16 scope global docker0
valid_lft forever preferred_lft forever
[root@test ~]# iptables -F my_chain
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
66 4512 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
0 0 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 13 packets, 1212 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT icmp -- * * 192.168.0.99 0.0.0.0/0 icmptype 0
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]# iptables -A my_chain -o enp2s0 -j ACCEPT
[root@test ~]# iptables -A INPUT -o enp2s0 -j DROP
iptables v1.4.21: Can't use -o with INPUT
Try `iptables -h' or 'iptables --help' for more information.
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
238 16280 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
0 0 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 61 packets, 5724 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT icmp -- * * 192.168.0.99 0.0.0.0/0 icmptype 0
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT all -- * enp2s0 0.0.0.0/0 0.0.0.0/0
[root@test ~]#
提示：同样-o表示匹配网络报文的出口接口，不能用于网络报文入口的链上。在iptables/netfilter框架中，报文的出口只经过FORWARD、OUTPUT和POSTROUTING这三个主链，即便我们在自定义链上用-o来指定匹配出口的网络接口，也只有被FORWARD、OUTPUT或者POSTROUTING这三个主链所引用才能生效，匹配到报文，用在INPUT或PREROUTING链上iptables是不允许的。可以看到FORWARD这个链上即可以匹配网络报文的入口接口和出口接口。
二、tcp/udp/icmp隐式扩展选项说明
iptables的匹配条件分基本匹配条件和扩展匹配条件，扩展匹配条件里有显示扩展和隐式扩展，从字面上很好理解，显示就是明确指定嘛 ，隐式就是不明确指定，通常扩展匹配条件是需要加载扩展模块（/usr/lib64/xtables/*.so）方可生效；隐式扩展我们可以理解为，当我们使用-p 去指定协议时无需再用-m再指定其模块，就可以使用其扩展模块中的选项，也就是说不需要我们手动的去加载模块，-p 所指定的协议，会帮我们加载。（这个仅个人理解哈）
1、tcp协议的隐式扩展选项说明
[!] --source-port, --sport port[:port]：匹配报文源端口,可为端口范围，当端口连续时可以用：来表示；比如21：25，表示匹配21，22，23，24，25这些连续的端口。
[root@test ~]# iptables -F my_chain
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
878 58520 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
0 0 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 13 packets, 1212 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT icmp -- * * 192.168.0.99 0.0.0.0/0 icmptype 0
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]# iptables -A my_chain -s 192.168.0.232 -d 192.168.0.99 -p tcp --sport 22 -j ACCEPT
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
1324 93312 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
0 0 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 34 packets, 3144 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT icmp -- * * 192.168.0.99 0.0.0.0/0 icmptype 0
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 192.168.0.232 192.168.0.99 tcp spt:22
[root@test ~]#
提示：以上添加到规则表示匹配源地址为192.168.0.232 目标地址为192.168.0.99 的tcp报文，并且源端口为22 的报文，如果匹配到这样的报文，给予放行操作。当然如果是匹配一个连续的端口可以写成：来表示中间连续的端口，它也支持对源端口取反，表示匹配除了指定的端口以外的所有端口如下所示
[root@test ~]# iptables -A my_chain -s 192.168.0.232 -d 192.168.0.99 -p tcp --sport 23:30 -j ACCEPT
[root@test ~]# iptables -nvL my_chain
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 192.168.0.232 192.168.0.99 tcp spt:22
0 0 ACCEPT tcp -- * * 192.168.0.232 192.168.0.99 tcp spts:23:30
[root@test ~]# iptables -A my_chain -s 192.168.0.232 -d 192.168.0.99 -p tcp ! --sport 40:50 -j ACCEPT
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
1519 107K ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:41319
0 0 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.99 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 13 packets, 1212 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT icmp -- * * 192.168.0.99 0.0.0.0/0 icmptype 0
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 192.168.0.232 192.168.0.99 tcp spt:22
0 0 ACCEPT tcp -- * * 192.168.0.232 192.168.0.99 tcp spts:23:30
0 0 ACCEPT tcp -- * * 192.168.0.232 192.168.0.99 tcp spts:!40:50
[root@test ~]#
[!] --destination-port,--dport port[:port]：匹配报文目标端口,可为范围，当端口连续是也可以用：来代替连续中间的端口，同--sport用法一样
[root@test ~]# iptables -F
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 19 packets, 1332 bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 13 packets, 1212 bytes)
pkts bytes target prot opt in out source destination
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]# iptables -A my_chain -d 192.168.0.99 -p tcp --dport 22 -j ACCEPT
[root@test ~]# iptables -A my_chain -d 192.168.0.99 -p tcp --dport 23:25 -j ACCEPT
[root@test ~]# iptables -A my_chain -d 192.168.0.99 -p tcp ! --dport 80 -j ACCEPT
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 19 packets, 1332 bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 13 packets, 1212 bytes)
pkts bytes target prot opt in out source destination
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:22
0 0 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpts:23:25
0 0 ACCEPT tcp -- * * 0.0.0.0/0 192.168.0.99 tcp dpt:!80
[root@test ~]#
[!] --tcp-flags mask comp表示匹配符合指定标志的数据报文，mask表示需检查的标志为列表，用逗号分隔，例如SYN,ACK,FIN,RST；comp表示mask列表中必须为1的标志为列表，没有指定表示必须为0用逗号分隔
[root@test ~]# iptables -F
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 22 packets, 1556 bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 15 packets, 1396 bytes)
pkts bytes target prot opt in out source destination
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]# iptables -A my_chain -p tcp --tcp-flags SYN,ACK,FIN,RST SYN -j ACCEPT
[root@test ~]# iptables -A my_chain -p tcp --tcp-flags ALL ALL -j DROP
[root@test ~]# iptables -A my_chain -p tcp --tcp-flags ALL NONE -j DROP
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 47 packets, 3830 bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 39 packets, 3630 bytes)
pkts bytes target prot opt in out source destination
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp flags:0x17/0x02
0 0 DROP tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp flags:0x3F/0x3F
0 0 DROP tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp flags:0x3F/0x00
[root@test ~]#
提示：以上规则表示匹配tcp报文，syn=1 其他标志位为0的报文给予允许放行，匹配所有标志位为1的报文给予丢弃，匹配到所有标志为0的报文给予丢弃。这个扩展选项也支持取反，表示出了指定的标志位的所有报文。
[!] --syn：用于匹配TCP第一次握手报文，它相当于--tcp-flags SYN,ACK,FIN,RST SYN
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 73 packets, 5582 bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 61 packets, 6538 bytes)
pkts bytes target prot opt in out source destination
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp flags:0x17/0x02
0 0 DROP tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp flags:0x3F/0x3F
0 0 DROP tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp flags:0x3F/0x00
[root@test ~]# iptables -A INPUT -p tcp --syn -j ACCEPT
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 11 packets, 804 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp flags:0x17/0x02
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 8 packets, 864 bytes)
pkts bytes target prot opt in out source destination
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp flags:0x17/0x02
0 0 DROP tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp flags:0x3F/0x3F
0 0 DROP tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp flags:0x3F/0x00
[root@test ~]#
2、udp协议的隐式扩展选项说明
[!] --source-port, --sport port[:port]：匹配报文的源端口或端口范围，当端口连续可以使用：来代替连续的中间端口
[root@test ~]# iptables -F
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 24 packets, 1636 bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 15 packets, 1396 bytes)
pkts bytes target prot opt in out source destination
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]# iptables -A OUTPUT -p udp --sport 928 -j ACCEPT
[root@test ~]# iptables -A OUTPUT -p udp --sport 111:123 -j ACCEPT
[root@test ~]# iptables -A OUTPUT -p udp ! --sport 323 -j DROP
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 14 packets, 1028 bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 10 packets, 1144 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 udp spt:928
0 0 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 udp spts:111:123
0 0 DROP udp -- * * 0.0.0.0/0 0.0.0.0/0 udp spt:!323
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]#
[!] --destination-port,--dport port[:port]：匹配报文的目标端口或端口范围，当端口连续可以使用：来代替连续的中间端口
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 73 packets, 5156 bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 54 packets, 6288 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 udp spt:928
0 0 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 udp spts:111:123
1 76 DROP udp -- * * 0.0.0.0/0 0.0.0.0/0 udp spt:!323
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]# iptables -A INPUT -p udp --dport 928 -j ACCEPT
[root@test ~]# iptables -A INPUT -p udp --dport 111:123 -j ACCEPT
[root@test ~]# iptables -A INPUT -p udp ! --dport 323 -j DROP
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 14 packets, 1028 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 udp dpt:928
0 0 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 udp dpts:111:123
0 0 DROP udp -- * * 0.0.0.0/0 0.0.0.0/0 udp dpt:!323
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 10 packets, 1160 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 udp spt:928
0 0 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 udp spts:111:123
1 76 DROP udp -- * * 0.0.0.0/0 0.0.0.0/0 udp spt:!323
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]#
3、icmp协议的隐式扩展选项
[!] --icmp-type {type[/code]|typename}
type/code 的值代表意义
备注：此图片来源网络
从上面的表可以看到不同的type，所表达的意思不同，就拿icmp最常用的两个类型，0和8来说，0表示icmp的应答数据包类型，就好比我们去用ping工具去探测远端主机是否存活，可以向远端主机发送icmp协议的8号类型的数据包，对方收到这种类型的数据包，如果正常存活，它会回复一个icmp0号类型的消息，否则它会恢复一个其他类型的数据包（通常情况在对方主机没有设置任何针对icmp协议报文的控制时）
在iptables里允许我们去ping对方，不允许对方ping我们
[root@test ~]# iptables -F
[root@test ~]# iptables -A OUTPUT -p icmp --icmp-type 8 -j ACCEPT
[root@test ~]# iptables -A INPUT -p icmp --icmp-type 0 -j ACCEPT
[root@test ~]# iptables -A INPUT -p icmp --icmp-type 8 -j DROP
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 25 packets, 1780 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 0
0 0 DROP icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 17 packets, 1580 bytes)
pkts bytes target prot opt in out source destination
0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 8
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]#
提示：把以上三条规则添加到iptabels中就可以实现我们本机发出去的icmp类型为8 的报文可以正常放行，从对方主机返回icmp类型为0的应答报文可以正常放行，同时明确指定发往本机icmp类型为8的请求报文给予丢弃操作
提示：这样是可以拒绝别人用ping工具来探测我们防火墙主机是否存活，当然这样设置后，我们自己想探测都不行了，要想设置自己可以探测，我们可以在规则里添加对应的规则。明确放行特定的icmp数据报文
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 30 packets, 2084 bytes)
pkts bytes target prot opt in out source destination
15 1260 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 0
35 2940 DROP icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 19 packets, 1780 bytes)
pkts bytes target prot opt in out source destination
36 3024 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 8
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]# iptables -I INPUT -s 192.168.0.151 -p icmp --icmp-type 8 -j ACCEPT
[root@test ~]# iptables -A OUTPUT -d 192.168.0.151 -p icmp --icmp-type 0 -j ACCEPT
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 8 packets, 528 bytes)
pkts bytes target prot opt in out source destination
12 1008 ACCEPT icmp -- * * 192.168.0.151 0.0.0.0/0 icmptype 8
15 1260 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 0
46 3864 DROP icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 8
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 5 packets, 764 bytes)
pkts bytes target prot opt in out source destination
36 3024 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmptype 8
0 0 ACCEPT icmp -- * * 0.0.0.0/0 192.168.0.151 icmptype 0
Chain my_chain (0 references)
pkts bytes target prot opt in out source destination
[root@test ~]#
提示：如果OUTPUT链的默认处理动作是DROP 需要配置以上两条规则，如果默认规则是ACCEPT 那么在INPUT链上添加一条允许指定源ip的报文允许就可以了
提示：可以看到添加了指定的源ip主机允许规则后，用对应的主机ping防火墙主机了。
以上就是tcp、udp、icmp这三种协议的常用隐式扩展选项。
作者：Linux-1874
本文版权归作者和博客园共有，欢迎转载，但未经作者同意必须保留此段声明，且在文章页面明显位置给出原文连接，否则保留追究法律责任的权利.
